In conventional systems of this type, the processing path is approximated by the output of one or more function generators. These function generators generate only analytic curves such as straight lines, circles, parabolas, etc. Relatively simple figures, such as rectangles with rounded corners may be formed by a combination of such outputs. The relatively complicated processing paths which appear very frequently in practice cannot be approximated in this way. The only available alternative is then manual operation or a numerical control system.